1. Field of the Invention
The present invention relates to a process for the production of a magnetic recording member by an electric field vapor deposition, more particularly, to a process for the production of a magnetic recording member having excellent adhesion and good magnetic properties by an electric field vapor deposition.
2. Description of the Prior Art
Hitherto, coating type magnetic recording members in which a powdery magnetic material such as fine particles of .gamma.-Fe.sub.2 O.sub.3, Co-doped .gamma.-Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4, Co-doped Fe.sub.3 O.sub.4, Berthollide compounds of Fe.sub.2 O.sub.3 and Fe.sub.3 O.sub.4, or CrO.sub.2, ferromagnetic alloys, or the like, is dispersed in an organic binder such as a vinyl chloride-vinyl acetate copolymer, a styrene-butadiene copolymer, an epoxy resin, a polyurethane resin, and the like, coated on a non-magnetic support, and then dried, have been widely used.
On the other hand, with recent increasing demands for high density recording, binderless magnetic recording members, in which a ferromagnetic metal thin film produced by vapor deposition such as a vacuum vapor deposition, sputtering, ion plating, etc., or by a plating such as electroplating, electroless plating, etc., is used as magnetic recording layers, that is, where no binder is used, have been attracting attention, and much effort is currently being directed to put such binderless magnetic recording members into practical use.
Since coating type magnetic recording members use, as magnetic materials, metal oxides having a lower saturation magnetization than ferromagnetic metals, the reduction in the thickness of the magnetic layer required for high density recording gives rise to a reduction in the signal output, and thus their uses are limited. Furthermore, such magnetic recording members have the drawbacks that their manufacture is complicated and large incidental equipment for solvent recovery or the prevention of pollution is required.
On the other hand, the binderless magnetic recording members have the advantages that a ferromagnetic metal having a higher saturation magnetization than oxides can be formed as a thin film in a state such that a non-magnetic material such as a binder is not present, thereby permitting the magnetic layer to be made thinner for high density recording; further, such can be manufactured by a simplified process.
Although binderless magnetic recording members where a ferromagnetic metal layer is provided as a magnetic recording layer are considered to be suitable for high density recording, particularly short wavelength recording, e.g., recording of short wavelengths reaching 1 .mu.m such as video signals, it has been difficult to produce such magnetic recording members having magnetic properties as are required in magnetic recording members with a ferromagnetic metal layer which has good adhesion to a support and is resistant to relative movement against a magnetic head.
For instance, it is known that by a vacuum vapor deposition a magnetic film having excellent magnetic characteristics can be produced by striking the vapor beam of a ferromagnetic material obliquely upon the support (see, for example, U.S. Pat. Nos. 3,342,632 and 3,342,633; W. J. Schuele, J. Appl. Phys., Vol. 35, 2558 (1964), D. E. Speliotis et al., J. Appl. Phys., Vol. 36, 972 (1965), etc.). The inventors' experiments have revealed, however, that the use of conventional vacuum vapor deposition methods generally results in insufficient adhesion between the magnetic layer and the support, and that although the application of a glow discharge, etc., to the support prior to the vacuum vapor deposition slightly increases adhesion, the adhesive properties deteriorate upon increasing the angle of incidence of the vapor beam obliquely upon the support, and thus the magnetic recording member obtained is not practically usable.
On the other hand, as a method of obtaining a magnetic film having high adhesion, vapor deposition in a glow discharge as discovered by D. M. Mattox (see U.S. Pat. No. 3,329,601), i.e., ion plating, is known. This method, however, suffers from the defects that, since this method is carried out in the vacuum region in which the average free path of the vapor particles is small, and the vapor particles are accelerated by means of an electric field perpendicular to the surface of the support near the cathode and deposited on the support, there cannot be obtained the effect of increasing the magnetic properties as can be obtained by oblique vapor deposition.